Cook ground beef in a large skillet over medium-high heat until browned, about 8 minutes. Break up the meat as it cooks. Mix in taco seasoning, salsa, and water. Stir and cook for another 2 minutes. Remove from heat.
Place a string cheese in the middle of a tortilla and add about 3 tablespoons of taco meat. Fold in the sides of the tortilla and roll up from one end to the other to make a log shape. Place on a baking sheet seam side down and repeat with the remaining ingredients.
Spray the taquitos with olive oil spray and sprinkle with chili powder.
Bake for 15 minutes on the top rack. (see note)
Remove from the oven and serve warm with guacamole, sour cream, and/or salsa for dipping.
Notes
If your taquitos aren't browned enough for your liking after 15 minutes, you can turn the oven to 425 degrees F and let them brown for another 5 minutes while the oven heats up. This gives the taquitos a crispy golden outside.